This application relates to hard disc drives and more particularly to an apparatus and method for coupling a disc to a hub, so as to dampen radial vibrations of the disc.
The storage medium for a disc drive is a flat, circular disc capable of retaining localized magnetic fields. The data that are stored upon the disc find physical representation through these localized magnetic fields. The data are arranged on the disc in concentric, circular paths known as tracks.
The localized magnetic fields can be detected by a magnetically sensitive head when they are brought in close proximity to the head. During operation the disc continually rotates, meaning that for each rotation, a head fixed a given radius from the center of the disc would encounter every localized magnetic field along a given track. Altering the radial coordinate of the head allows the head to read or write data along a different track.
The head is mounted upon an actuator arm that is rotated by a servo control system. Accordingly, the track position of the head is controlled by the servo system. During a read or write operation, for example, the servo control system ensures that the head remains oriented over the proper track, a function known as xe2x80x9ctrack following.xe2x80x9d The more accurately track following can be performed, the closer together the various tracks on the disc may be spaced, resulting in greater information density. Increased accuracy in track following also permits a higher rotational speed for the disc, resulting in faster access to information stored thereon.
One factor that renders track following less precise is the presence of radial vibrations. Radial vibrations cause the disc to move relative to the head, thereby moving the head away from the center of the particular track it is following. Radial vibrations may result from imperfections in the bearings interposed between the rotating and stationary members of the spin motor in the disc drive. These imperfections cause the rotating member (the hub) to vibrate radially as it rotates; in conventional disc drives, the disc is rigidly mounted to the hub, meaning that vibration of the hub results in vibration of the disc. Generally, the faster the disk rotates, the more pronounced the radial vibrations. Other sources of radial vibrations include windage effects that act upon the disc as it rotates and accident jarring of the disc drive itself.
If radial vibrations of the disc could be attenuated, track following could be performed with greater precision. Benefits, such as increased information density and increased rotational speed of the disc, may be realized by such attenuation. Accordingly, there is a need for an apparatus or method for reducing radial vibrations within disc drives.
Against this backdrop the present invention has been developed. The apparatus includes a hub that rotates, which is coupled to a magnetically encodable disc via a flexible joint. The flexible joint may be made of a viscoelastic adhesive. There exists no rigid coupling between the disc and the hub, meaning that radial vibrations of the hub result in compression or decompression of the flexible joint, rather than in translation of the disc.
Another embodiment of the present invention involves applying a viscoelastic adhesive to a hub, and applying a disc to the viscoelastic adhesive without otherwise rigidly coupling the disc to the hub.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.